Media captionMr Smyth told the BBC he believed Fermanagh and South Tyrone was an Ulster Unionist seat

A former Ulster Unionist MP has said the DUP should step aside in Fermanagh and South Tyrone and allow the UUP a free run in the general election to try and oust Sinn Féin's Michelle Gildernew.

Rev Martin Smyth, who stood down as the MP for South Belfast in 2005, said the DUP and the UUP should co-operate in order to maximise the unionist vote.

He told the BBC that his former constituency in Belfast should either be a UUP or DUP seat.

Mr Smyth's comments came as discussions continue between the DUP and the UUP about a general election pact.

'Historic ties'

Speaking to the BBC's The View programme, Mr Smyth said: "Fermanagh looks to me more like an Ulster Unionist seat, whereas South Belfast can take a DUP or an Ulster Unionist because of the historic ties with Ulster Unionism in Fermanagh."

The former MP added: "I know Fermanagh a bit and I would have thought speaking frankly that seemed to me the seat for the Ulster Unionists."

Mr Smyth was the last Unionist MP to win South Belfast and after he retired, the SDLP's Alasdair McDonnell captured the constituency.

Alasdair McDonnell retained the seat in 2010, securing 14,000 votes, but Sinn Féin did not run a candidate.

However, in this election, Sinn Féin have selected former Lord Mayor of Belfast Máirtín Ó Muilleoir.

In the 2005 and 2010 elections, both the UUP and DUP ran candidates that resulted in the unionist vote being split.

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Political analyst Henry Bell said if unionists split the vote in south Belfast again, a single nationalist candidate could take the seat

Political analyst Henry Bell has studied recent election results in south Belfast. He was asked if a joint unionist candidate could wrest the seat away from the SDLP.

He said: "With one single unionist candidate undoubtedly. The problem is unionists really gave the seat away by splitting the vote in 2005 and in 2010 that was compounded by the fact that there was a single nationalist candidate - and that is what will dictate what will happen in this seat."

'Undemocratic'

Election pacts and understandings between unionists are not new.

In the 2013 by-election, the DUP and the UUP fielded Nigel Lutton as a unionist unity candidate.

The move prompted South Down MLA John McCallister to leave the Ulster Unionists. He told the BBC that electoral pacts are "undemocratic".

He said: "They are done purely on the basis of a sectarian head count and it drives the 'us and them' politics and that is very unhealthy for us as a society."

The DUP and the UUP are talking about a potential pact in certain constituencies, but despite many hours of discussions have not reached an agreement.

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The Alliance Party's Naomi Long exceeded all expectations when she took the East Belfast seat in 2010

Last weekend the DUP leader Peter Robinson confirmed that he was examining a potential deal that looked at around six seats.

He said: "I think there could be a fair deal between those six constituencies with the two parties, but we have to reach agreement."

Tactical voting

For the UUP, Danny Kennedy said he hoped party interests would not make it impossible to achieve agreement.

"I think we are running out of time on this issue to try and get the matter resolved," he said.

UUP leader Mike Nesbitt has warned that Belfast could be left without a unionist MP if a deal is not in place.

Mr Smyth said if a formal pact is not possible in certain constituencies, unionist voters will vote tactically.

He said: "I believe the unionist people in Belfast will vote for the party that they believe will win the seat.

"I know there will be staunch Ulster Unionists and staunch DUP members who are so narrow in their conceptions they would vote for no other unionist."

'Two-horse race'

The retired politician added: "I would have thought that wiser unionists will vote for the unionist that they believe will win the seat."

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Unionists are discussing whether to run a joint candidate in North Belfast, where Nigel Dodds came top in 2010

Two of the seats currently being discussed by the DUP and the UUP are North Belfast and East Belfast.

In 2010 in North Belfast, the DUP's Nigel Dodds polled 14,812 votes, with Sinn Féin's Gerry Kelly on 12,588.

Henry Bell said the election in May will be a two-horse race.

"It can only be won by Sinn Féin or the DUP and that is going to dictate what happens even if there is no pact there," he said.

"I think you are going to get unionists tactically voting as it already happened with Dodds."

On the electoral fight in East Belfast, Mr Bell said the Alliance Party's Naomi Long had exceeded all expectations back in 2010.

He said: "Naomi Long is very good at bringing in votes now. If she holds that seat she will do it by the following tactic - she will need to move her vote over the 40% mark to be safe and she would need the unionist vote to fragment."

Five years ago, the political map of Belfast changed. In two months' time, we will discover if it needs to be redrawn again.